Direct attached storage (DAS) is a storage topology in which each initiator, such as a server computer, is directly attached to storage devices, such as disks. In DAS topology systems there is no intervening network between an initiator and the storage device. An initiator may contain a host bus adaptor connected to the storage devices. Access to the storage devices is through the host bus adaptor.
Storage area network (SAN) is a storage topology in which initiators are connected to a storage network. For example, the storage network may be a fiber channel network. Also connected to the network may be storage devices, such as disks. An initiator may contain a host bus adaptor, such as a fiber channel adaptor, to connect to the storage network. Access to the storage devices is achieved through the storage network.